1. Technical Field
The present invention relates to automatic speech/speaker recognition (ASSR), and more particularly to an ASSR technique using a portable acoustic coupler or interface for remotely accessing an ASSR server over a communication channel such as a telephone line.
2. Discussion of Related Prior Art
In typical client/server or subscriber/service provider systems in which resources in the central server or service provider are accessed by numerous clients or subscribers, some form of client/subscriber authentication technique is used to verify that the client/subscriber is a valid system user. In many such systems, the authentication code, such as a PIN (personal identification number), keyword, or password is communicated by keying in a code or communicating in text to an operator. In some systems, the authentication code is by voice, i.e., the code is spoken into the server. The server (in this case, an ASSR server) recognizes the speech utterance and compares it against stored valid voice authentication codes to authenticate that the user is a valid client.
In ASSR server/client systems, it would be convenient if a client is able to remotely communicate his authentication code by voice over a communication channel such as a telephone line, making possible the capability for any client to have access to the server wherever a telephone line is available. The telephone line may be a land line or cellular line. In the cellular case, access to the server is completely portable, i.e., whenever and wherever a cellular phone and a cellular connection are available.
Operational difficulties associated with telephonic ASSR systems such as one described above include (1) loss of accuracy due to degradation of voice data when it is sent over telephone lines, and (2) the varied background noise characteristics at the user end depending upon the location of the telephone from which the user is calling, such as when a caller is calling from a street phone or when he is driving a car, etc. Both situations result in either data or signal integrity loss and thus severe reduction in the accuracy in recognition of the speech/speaker.
This loss of data and recognition accuracy problem can be reduced or eliminated if speech signal preprocessing (SSP) is performed at the client's end prior to the signal being sent over the telephone line to the server. SSP includes characterizing the acoustic features of the transmitting device, environment, speaker, and the communication channel. The SSP information is processed by the ASSR server to set references, select appropriate decode models and algorithms to recognize the speaker or decode the speech by modeling the channel transfer function and the background noise to reduce word error rate of the speech or to accurately perform speaker recognition. However, to perform SSP at the user's end, one would need SSP equipment including a computer having SSP software. Such SSP capability is generally absent in present standard telephones or network computers (NC).
Therefore, there is a need for a portable SSP device which is compact in size and light in weight for ease of transport, capable of coupling onto any telephone or a data communication device and includes capabilities for facilitating accurate speaker recognition when accessing the ASSR server over the communication channel and throughout the interaction with the server, and for accurate speech recognition communication between the portable SSP device and the ASSR server.